Another advert offers a "porcelain paradise" just off the main parade route, for $3 per visit.

The advert reads: "Imagine, you, gazing at passing floats. Now imagine you gazing at more floats just a few minutes later. Because that's all it will take for you to unleash your bowels in our frequently cleaned porcelain paradise."

The app's founders have a history of creating public-service-minded apps.

One of them, Travis Laurendine, has been recognised by the White House for efforts in "hacking" for a civic cause.

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The app will help stop the number of illegal "rogue pees", the creators say

More than 10 million people have booked rooms using AirBnB, a popular alternative to using a hotel.

While Uber allows people to use their own vehicles to provide taxi rides.

These types of services - dubbed the "sharing economy" - rely on the principle that allowing users to easily vote on how good a service is will ensure high quality.